Track-type work machines are in widespread use in construction, mining, forestry and similar industries. Bulldozers, cranes and large agricultural tractors are familiar track-type work machines along roads, freeways and at construction sites. “Tracks” rather than wheels are typically used on work machines operating in environments where creating sufficient traction with conventional tires is problematic or impossible. Rather than rolling across a work surface on wheels, track-type work machines utilize one or more tracks extending about a plurality of rotating components. Such tracks are typically made up of a loop of coupled metal links having outer sides that engage the ground or work surface, and inner sides traveling about the rotating components, which can include various drive sprockets, tensioners, idlers and “track rollers.” The track rollers of a typical track-type work machine rotate passively against an inside of the track as it traverses the work surface. In one common design, the rollers include circumferential channels that engage with a “rail” extending along an inside of the track links.
Work machines often operate in particularly rugged environments, including bedrock, refuse mounds, gravel, and uneven soil or other types of terrain. As the work machine traverses rough or uneven ground, or turns on a rugged work surface, the track rollers can be subjected to substantial loads. For example, where the work machine passes over boulders or other rigid objects, the load distribution among the rollers can be altered. Similarly, the lateral load carried by one or more of the rollers can vary where the track passes over an obstacle or uneven surface. In some instances, the loads encountered by the track rollers can be sufficient to damage or break the rollers themselves, or bearings and bearing seals associated with the same. Thus, each individual roller is typically quite rugged to allow it to bear loads of varying type and degree.
An individual roller typically includes a rim, which may be fashioned from one or more rim portions, rotatable about a bearing assembly. In one known design, a hard, metallic roller rim is rotatable about a hard, metallic shaft fixed relative to the roller frame, the rim being rotatably supported on one or more relatively softer sleeves press-fitted into a bore in the rim and rotatably fixed relative thereto. Lubricating fluid is typically disposed along the shaft and sleeve(s), and retained within the rim by seals at opposite sides thereof. Despite relatively rugged designs, when the work machine track rollers encounter certain loads, various of the components, or regions thereof, may disproportionately bear much of the load on the track roller. For instance, certain loads on a track roller may be borne predominantly by an edge portion of the sleeve. In such cases, a deflection of the rim relative to the shaft has a tendency to impinge upon an outside edge portion of the sleeve bearing that supports the track roller. In addition, ends of the sleeves are often positioned adjacent a thrust bearing mounted in the rim and retained therein with a separate retainer assembly. Damage or excessive wear of the sleeves and other components can result over time, and/or frequent servicing may be required.
In an attempt to minimize servicing and repairs, engineers have continually refined the design, manufacturing and assembly techniques of track rollers. In certain designs, relatively large clearances for the bearing assembly components address the above concerns. The sleeve may be formed having an inner diameter with a relatively large clearance about its respective shaft. A degree of wobble in the sleeve, due to large clearances, and robust bearing components, can prolong the service life of certain of the components.
One drawback to many prior art designs, however, is that it is generally necessary to align the track roller rim portions to fairly exacting specifications. Even small misalignments between adjacent track roller rim portions can affect the performance of the bearing assembly and bearing seals. Because a common shaft typically extends through both roller rim portions, misalignment between the respective bores has a tendency to cause misalignment between the rim portions and the shaft. In other words, even small misalignments between the bores can cause the respective shaft and bore axes to be out of alignment. Consequently, rotation of the roller, and in particular, uneven loads on the roller can cause edge portions of the sleeves to bear a disproportionate part of the load and wear. Thus, unless the components are manufactured and assembled with relatively close tolerances, edge loading of the bearing can eventually result in premature failure.
Other problems with known designs relate to the relatively large size of the bore passing through the track roller rim portions, in particular the challenge in effectively sealing the bore to retain lubricating oil therein. A larger bore diameter may require more complex, and less reliable sealing. In addition, retainers for thrust bearings must be bolted into the rim portions. Not only is the design thus relatively complicated, but additional bores for the retainers are required in the rim. The combination of large clearances between bearing sleeves and shafts, and additional bores for the retainers consumes a significant amount of the rim volume. Over the course of many working hours, a portion of the rim volume wears away. Reducing this available wear volume in many designs contributes to the requirement of unduly frequent replacement.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.